Fluidized multistaged reaction system for polymerization

ABSTRACT

This invention relates to a novel horizontal fluid bed reactor, which in a single unit, provides for the polymerization of monomer to polymer and mixed monomers to co-polymers. Within one reactor shell the reactor contains a plurality of polymerization stages which permit the achievement of narrow residence time distribution of the produced polymer. This arrangement also creates a sufficiently tight subdivision of the reactor volume which permits a plurality of gas circulation stages of different gas compositions, as well as, polymerization temperatures.

This application is a continuation, of application Ser. No. 07/946,912,filed Oct. 15, 1992 now abandoned, which is a divisional of applicationSer. No. 708,747, filed May 31, 1991, now U.S. Pat. No. 5,169,913.

BACKGROUND OF THE INVENTION

The application of a single stage (back mix) gas phase fluid bed reactorfor the production of widely used polymers, is well established as aleading technology in the plastics industry.

In a typical single stage fluid bed polymerization reactor, thefluidized bed is finely divided polymer formed from the monomer gas,which is the fluidizing gas of the reactor. Both the monomer gas and thefinely divided catalyst are continuously fed to the reactor, which ismaintained at controlled conditions of pressure and temperature, and thepolymer continuously formed discharges from the reactor at the rate thepolymer is formed.

The polymer yield on the catalyst fed is a function of the residencetime of the catalyst particles in the reactor. Since the typical singlestage fluid bed polymerization reactor is a continuous back-mix reactor,the residence time distribution of the catalyst particles follows anexperimental decay relationship. In other words, it is extremely broad.

In a typical operation, the unreacted monomer fluidizing gas dischargedfrom the reactor is cooled, its composition reconstituted with freshmonomer fluidizing gas to maintain a constant steady-state, compressed,and returned to the fluid bed polymerization reactor as the fluidizinggas.

In the production of more complex polymers and co-polymers, it is knownpractice in the plastics industry to use more than one, typically two orthree, back-mixed fluid bed reactors in series to permit changingmonomer gas composition and polymerization conditions of temperature andpressure at different points in the polymerization reaction cycle toachieve desired polymers.

Typically, each back-mixed fluid bed reactor is separated from itsadjacent units through feed and discharge locking devices. Each reactoris served by its own independent gas recycle and recompression system sothat each reactor can be run on independently different compositionsand/or combinations of monomer fluidizing gas. Since this approach isbased on the polymer exiting one system and feeding to the next systemin series, it has been found necessary to provide for a significantpressure drop from system to system (i.e. reactor to reactor), typicallybetween 50 to 100 psig, to facilitate the transfer of the polymerpowder.

In addition, since each back-mixed reactor system is a separate entity,the capital cost of a system of this type is high. Typically, the numberof back-mixed reactors in series in a commercial installation has beenlimited to two or three systems by economic considerations despite thefact that there is increasing indication that a larger number of unitsin series to control residence time distribution and/or provide forflexible polymerization conditions would be advantageous. It has beenrecognized in many polymerization systems, for the production of themore complex co-polymers, that staging monomer changes in thepolymerization reaction results in superior properties such as tearstrength and puncture resistance in films, as well as, improved impactstrength combined with flexural strength in plastic injection moldings.There are a number of polymer products that can only be made by amulti-staged polymerization process.

This situation is further demonstrated by the fact that there areexamples of multistage polymerization reactor systems being used toadvantage in processes other than the gas phase fluid bed processingapproach.

A multi-stage polymerization system using a liquid diluent to suspendthe polymer, as opposed to utilizing gas phase fluidization and passingthrough a plurality of agitated reactors is described in U.S. Pat. No.3,454,675. This liquid phase processing system, when applied to suchco-polymers as propylene-ethylene, has the obvious disadvantage ofdissolving the portion of the co-polymer that is soluble in the liquiddiluent, thereby reducing yield of polymer when the liquid is removed.

Another reaction system for co-polymerization that has some commercialapplication is a horizontal stirred reactor which depends on mechanicalagitators to transport the polymer through the reactor to the dischargeport, while the reaction is conducted in the vapor or gas phase. Somestaging of the polymerization is claimed by this system, but it islimited to a single gas phase composition. One such system is describedin U.S. Pat. No. 4,710,538. While benefit is obtained by the staging ofthe polymer flow through the horizontal reactor, the process requiresthe expending of excess energy in order to mechanically agitate thecontents of the reactor. The process is also not very adaptable since asingle monomer gas is all that can be provided to the reactor.

SUMMARY OF THE INVENTION

This invention is directed to horizontal fluid bed reactor and processfor the use of same in polymerization reactions. The bed reactor is asingle unit providing for the polymerization of monomer to polymer andmixed monomers to co-polymers. Within one reactor shell the reactorcontains a plurality of polymerization zones which in turn are furthersubdivided into stages permitting the achievement of a narrow residencetime distribution of the polymerized material, which approaches plugflow through the bed. As each zone can be made individual andindependent of the other zones, a plurality of gas circulation stages ofdifferent gas compositions is possible, such individuality permitting acomposition of gaseous monomer individual to each zone. Also, otherconditions of polymerization are variable, such as pressure andtemperature.

The progressive flow of polymer through the plurality of stages within asingle gas flow stage, as well as the flow through the plurality of gasstages benefits the properties of the ultimately produced polymer, aswell as process economics.

Generally describing the process, a fluid bed polymerization process forproducing polymers from primarily gaseous monomers is conducted bypassing gas streams containing one or more reacting monomerscontinuously through a fluidized bed reactor in the presence of asuitable catalyst. After the gas stream passes through the fluid bed, itcontains unreacted monomer and other gas phase contaminates andmodifiers. It is withdrawn from the reactor via a recycle system wherethe gases are cooled, compressed, the necessary make-up gases added (eg:fresh monomer gas), and then recycled to the reactor. The formingpolymer particles in the reactor, maintained in a fluidized state by theflowing fluidizing gas, passes in series from polymer stage to stage andzone to zone is withdrawn from the last zone as polymerized productwhich is then subjected to a degassing and catalyst deactivationtreatment.

Because each zone is suppliable with its own gas stream, and thecomposition of that gas stream can be selected independently of the gascompositions of the other zones, and because each zone is substantiallyan environment independent of the other zones, copolymerized polymerproducts are possible.

Each zone is subdivided by a series of baffles which preferably haveopenings on their sides and arranged to provide for a serpentine courseof flow. This arrangement, plus the number of baffles and zones used,create a narrow residence time distribution which approximates plugflow.

The innovative polymerization system of this invention is particularlywell suited for gas phase polymerization reactions involving one or moremonomers that are staged in order to effect changes in gas compositionor in physical conditions, such as temperature. However, a significantbenefit is also derived from the multistaged flow path of the polymer,particularly when using a heterogeneous catalyst, since there is asignificant improvement in yield and reaction rate due to the narrow,more uniform residence time distribution of the reacting particles inthe multistage reactor of this invention.

It is particularly well suited for the polymerization of blended blockcopolymer of olefins, which are formed by polymerizing a second monomeronto a polymer first formed by another monomer as described in U.S. Pat.No. 3,454,675, incorporated herein by reference.

While not limited to any particular type or kind of polymerizationreaction, this invention is suited to the polymerization of one or moreof the monomers listed as follows:

1. Olefin type such as alpha olefin monomers having two to eight carbonatoms. Some examples are --ethylene, propylene, butene, pentene,methylpentene, hexene, styrene and octane;

2. Polar vinyl monomer type--vinyl chloride, vinyl acetate,methylmethacrylate, tetraflouroetheylene, vinyl ether, acrylonitrile;

3. Diene type;

4. Acetylene type; and

5. Aldehyde type.

Catalysts generally employed in fluid bed polymerization of the abovemonomers usually are:

1. Coordinated anionic catalyst;

2. Cationic catalyst for co-polymerization with ethylene only: others ofthis type require free radical catalyst;

3. Either a free radical catalyst or a coordinated anionic catalyst; and

4. An anionic catalyst.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view of the single shell reactor system ofthe preferred embodiment.

FIG. 2a is a view of the zone subdividing walls of the preferredembodiment.

FIG. 2b is a cross sectional view of the zone dividing walls of thepreferred embodiment.

FIG. 3 is a perspective view of the zone dividing walls and closuremeans therefore of the preferred embodiment.

FIG. 4 shows the distribution of residence time around average residencetime in a zone for the particle residence time distribution for the fourstages within a zone.

FIG. 5 shows the particle residence time around the average residencetime in the reactor.

FIG. 6 is a view depicting the baffles of the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the multistaged single shell reactor of this invention is notlimited to any specific type of polymerization reaction, the detaileddescription of the operation of this reactor is directed to thepolymerization of the propylene based ethylene co-polymer. It isillustrated in FIG. 1 by a single shell reactor 10 with three fullcompartment separations, 31A, 31B, 31C to provide for three independentgas recirculation systems 44A, 44B, 44C, with each compartment or zoneseparation containing three polymer stage baffles to form four stagesper zone, 60 A, B, C, and D in Zone 31A, 60 E, F, G, and H in Zone 31B,and 60 I, J, K, L in Zone 31C. Each of the three zones and gas recyclesystems can be operated at different gas monomer compositions andtemperatures to achieve various combinations and characteristics ofpolymer or co-polymer.

In a typical application, catalyst particles and/or catalyst particlesplus polymer are continuously fed through feed port 58, at the feedzone, 59, which feeds into first stage 60A of the first zone 31A, andthen on to successive stages. The multistage arrangement in each zone,(eg: stages 60A, B, C, and D of Zone 31A) facilitates a narrowerresidence time distribution of the fluidized particles in the particularzone. As the number of stages within a zone increases from one toward aninfinitely large number, the residence time distribution function of theparticles within the zone changes from a broad exponentially decayingfunction to a narrow plug flow distribution, with all particles havingequal residence time in the zone.

The passage of fluidized polymer from stage to stage within a given zoneas shown in FIG. 1 is typically accomplished by providing alternatingpassage ports upon the baffles as shown in FIG. 6, to accomplish thecontinuous flow. This creates a serpentine course for the fluidizedpolymer to flow. By way of example, passage ports 61B and 62B are shownfor baffles 61A and 62A. These ports appear at opposite ends of thebaffles adjacent opposite side walls of the reactor vessel, and providea means for a serpentine course of flow.

Since there is a continuous feed at the feed end of the unit, plusadditional polymer being formed within the stages of the successivezones, the growing weight, and as well as the bed levels in the zones,provides the driving force to keep the fluidized bed of solids movingtoward and then through the discharge zone of the unit, 56, and then outthrough the discharge port of the vessel, 57.

In the illustrated example of FIG. 1 with three zone subdivisions, eachcontaining four stages, the zone subdividing walls 64A, 64B, and 64C,are sealed to the shell wall in the plenum volumes 32A, 32B and 32C, inthe fluid bed; and in the freeboard volumes above, the fluid bed 31A,31B, and 31C, and thereby keeping the fluidizing gases and gases to berecycled separate from the respective gases of each adjacent zone.

The fluidized bed of polymer and catalyst pass from one zone to theadjacent zone as shown in FIGS. 2a and 2b (representatively shown atzone wall 64A) through ports 55A, 55B and 55C in 64A, 64B, and 64C,respectively. The ports are preferably located below the surface of thefluid bed near the level of the distributor plate, 69. By limiting theratio of the area of the ports to the area of the separating wall 64A toa range of 1% to 2%, the extent of leakage of gas phase between adjacentzones, 31A and 31B for example, can be typically limited to 3% to 5% ofthe gas flow rate being circulated in the recycle systems serving eachzone.

For situations requiring even less gas mixing, the fluid bed flow portscan be equipped with closures as shown in FIG. 3 They are shown withrespect to flow ports 55A zone dividing wall 64A but are likewisepresent at 64B and 64C. In these cases, the ports are opened on a timedcycle by periodically opening the closures to facilitate thesemi-continuous flow of the fluid bed polymer and catalyst. The openingand closing can be accomplished, for example, using the sliding rod 81and closure 80 in FIG. 3 to open and close port 55A. Mechanical, manual,or other known means can be provided to drive the closure system. Suchan arrangement can so limit gas mixing between stages to 0.5% to 2%.

In a typical application, the catalyst particles and/or catalystparticles plus polymer continuously fed through feed port 58 at feedzone, 59, continuously flows into successive reaction stages 60 A, B, C,D, then 60 E, F, G, H, then 60 I, J, K, L. In the reaction zones andwithin the stages, the growing and formed polymer particles arefluidized by the continuous flow of the gas stream which containsmonomers. Fluidizing gas enters each zone, respectively at 75A, 75B and75C. The fluidizing gas streams consist of the recycle gas from recyclesystems 44A, 44B, and 44C, the make-up monomer gases from 70, 71, and72. Make up monomer gas lines 70, 71, and 72, join the recycle system44A, 44B, and 44C through supply lines 70A, 70B, 70C, 71A, 71B, 71C,72A, 72B, and 72C, along with any necessary polymer modifiers or diluentgases. The plurality of make up monomer gas lines (70A, 70B, 70C, 71A,71B, 71C, 72A, 72B, and 72C), each of which can contain a differentgaseous monomer or composition, permit the process operator to selectthe composition of the monomer gas separately and independently for eachzone. A fluidized bed is maintained by controlling the circulating gasrate to maintain a suitable fluidization velocity dependent on the sizeand density of the particles in given reaction zone.

To start up the reactor, the reaction zones 31A, 31B, and 31C arecharged with polymer particles before gas circulation. Preferably thispolymer may be close to the composition of the polymer to be formed whenthe reactor is running under steady-state conditions. The partially ortotally activated catalyst and/or catalyst with polymer particles istypically fed through feed port 58 at feed zone 59 from a supply tank(not shown) which is blanketed with a gas which is inert to thereactants. The feed is introduced into the first polymer stage, 60A,through the feed port 58 and through the feed zone 59.

Pressure drop of the fluidizing gas flowing through the polymer bed is afunction of the weight of the polymer bed divided by the cross sectionalarea. As the bed depth of conventional single stage vertical fluid bedreactor is approximately five times greater than that of the horizontalreactor of this invention. The present invention provides for a muchlower pressure drop than such reactors. As noted, make-up feed is addedto the circulating gas stream through lines 70, 71, and 72. The amountof make-up gas is determined by a conventional gas analyzer whichmeasures the composition of the recycle streams 44A, 44B, and 44C andadjusts the feed streams (75 A, B, and C) to maintain the desired gasphase composition.

The fluidizing gas streams to the reactor that do not react whilepassing through the polymer bed become the off-gas recycle streams. Inpassing through the freeboard volume above the bed, the entrainedpolymer is disengaged and falls back to the bed. In some cases, anyadditional entrained polymer is filtered from the gas stream andreturned to the bed. Each recycle gas stream after leaving the reactorthrough exit ports 52A, 52B, 52C is cooled in heat exchangers (51 A, B,and C) shown in FIG. 1 then pumped with compressors (50 A, B and C),mixed with the make-up gases to adjust composition, and returned to thereactor. The sequence of cooling and compression can be reversed whenthis proves economically advantageous.

Polymerization reactions of the monomers that this invention isapplicable to are exothermic. Therefore, it is necessary to remove theheat of reaction from reaction stages 60A through L, to maintain thepredetermined required polymerization temperature level in each stage toachieve desired polymers. This is accomplished by cooling the fluidizinggas stream and using the heat capacity of the fluidizing gas stream toremove heat from the fluid bed. The temperatures of the fluidizing gasentering feed ports 75 A, B, and C are kept sufficiently below the fluidbed temperature in the respective stages to accomplish the requiredenergy balance of the zone. The fluidizing off-gas discharging from thefluid bed into the freeboard volumes 31A, 31B, and 31C is very close intemperature to the temperature of the respective fluid beds in eachstage due to the intimate contact of the fluidizing gas with the highsurface area of the catalyst and polymer particles.

Polymerization rate is a function of catalyst concentration, partialpressure of reacting monomers, and temperature. Polymer yield for agiven catalyst is also a function of residence time in the reaction zonefor each particle.

In addition to the temperature control in the reaction zones maintainedby the previously described cooling capacity of the fluidizing gas, theheat of reaction release rate is limited by the feed rate of catalystand catalyst plus polymer to the fluid bed reactor. In most cases, thetemperature in the reaction zones are programmed to achieve particularpolymer properties. Pressure is controlled at a sufficiently high levelto achieve the highest possible rate consistent with the ability of thesystem to maintain a heat balance.

The polymer bed which consists of particles increasing in size as thepolymerization proceeds flows through the reactor zone around eachbaffle and through the slots 55A, 55B, 55C in each zone dividing wall(64A, 64B and 64C). These slots, illustrated by way of example in FIG. 3for 64A and 55A but also found at 64B/55B and 64C/55C are located justabove, or in the vicinity of, the distributor plate 69. The area andlocation of these slots are selected so as to minimize the gas mixingbetween zones, as well as, to facilitate the transport of the polymerthrough the walls between each gas stage.

In the multistage horizontal reactor of this invention, the pressuredrop driving force from stage to stage which maintains flow of polymeris accomplished by the fluid bed level at the feed end of the reactorbeing slightly higher in level than at the overflow port. This isanalogous to hydrostatic head which maintains the flow of a liquid in along channel. Typical level increases are of the order of 2 to 4 inchesof water column per twenty feet of reactor length. In the same way, whenthe fluidized polymer and catalyst particles pass through the slots inthe zone separation partitions 61A, 62A, 63A, 64A; 61B, 62B, 63B, 64B;61C, 62C, 63C, 64C, the pressure drop is of the order of 0.2 to 0.5inches of water column which is reflection in an equivalent drop influid bed level between successive zones.

The typical amount of gas phase mixing between adjacent independent gasrecycle systems 44A, 44B, 44C due to flow of gas phase through thesetransfer slots 55A, 55B, 55C has been estimated to be less than a rangeof 3 to 5 per cent of the gas circulation rate in the gas recyclesystem. However, closing these ports on a timed cycle using themechanical damper 80 shown in FIG. 3, is estimated to reduce the gasmixing through these ports to a range less than 0.5 to 2 per cent of thegas circulation rate. This feature may prove quite beneficial whenperforming polymerization reactions requiring large compositiondifferences between adjacent gas recycle zones to achieve particularpolymer properties.

The temperature of the fluid bed should be kept below the temperature atwhich the polymer particle will agglomerate or fuse together. In generalthe homopolymers have a higher fusing temperature than theircorresponding co-polymers.

The fluid bed reactor may be operated at a pressure of up to a 1000psig, but for polyolefin resins pressures from 100 to 400 psig aresufficient to achieve required polymerization reaction rates. Operationat the higher pressure levels permit higher polymerization reactionrates since an increase in pressure benefits both the polymerizationrate due to higher partial pressure of monomer, and the heat removalrate by the discharging fluidizing gas due to the higher heat capacityof the denser gas phase.

On discharge of the polymer product from the reactor it is preferable toseparate the gas fluid from the polymer particles and return the fluidto the recycle stream, generally referred to as "degassing". There areseveral ways known to the art to do this. The multistage reaction systemof this invention permits effective degassing the fluid from thepolymer. To add this feature, it is only necessary to provide a separatefinal gas stage operating with inert gas as the fluidizing gas, andrefrain from any monomer make up to this recycle stream. This will causethe residual monomer in the polymer to polymerize, thereby the polymeris made free of monomer entrainment to minimum concentration.

The use of the baffle maze to form the required number of stages withina zone serves to control the residence time distribution of the reactingparticles. As the number of stages in each zone increases from one tothe four shown in FIG. 1 or even a greater number, the residence time ofthe particles in each zone become more uniform approaching the ultimate,i.e. plug flow.

A uniform residence time of particles through the several stages of themultistage reactor results in several important polymer properties, aswell as, the improvement in yield of product from any given reactionsystem. In the horizontal multistage reactor, each discrete polymerparticle has a residence time to contact with the circulating gas closerto the average of all particles. Therefore, a more uniform compositionresults. In contrast, in a conventional single stage vertical fluid bedreactor the path of polymer particles is subject to what is termedback-mix agitation. In such a reactor the discrete polymer particle hasa statistical residence time which is a decaying exponential functionwhich is very broad; i.e., the residence time of reaction from particleto particle is very different. Improvements in catalyst utilization(yield of polymer per unit mass of catalyst) can exceed 20% as a resultof uniform reaction residence time in a heterogeneous catalyst reaction.

Because of the more uniform exposure of the polymer particle to thecirculating gas in the horizontal multistage reactor the control ofstickiness experienced when producing co-polymers is materiallyimproved. Due to the narrow residence time distribution in this reactorthe polymer uniformly formed in the first gas phase contains fewer"short reaction time particles" and will develop less stickiness as itprogresses through the succeeding gas stages to form the desiredcopolymer from the monomers and co-monomers.

The benefit of pressure on the polymerization reaction was mentionedearlier. In the single shell multistage reactor there is negligiblepressure drop between gas recycle zones (differentials in terms ofinches of water). However, in single stage vertical reactors used inseries there must be a significant pressure drop to facilitate thetransfer out of one reactor into the succeeding unit. Pressure drops of50 to 100 psig are usual. Elimination of this large stage to stagepressure drop in the single multistage reactor results in an advantageof 20 to 40 per cent in reaction rate due to the higher averageoperating pressure in this reactor; i.e., higher productivity per volumeof reactor (higher space time yields).

In addition, the cost of construction of a facility using a single shellmultistage reaction system for the production of such co-polymers as aremade from the lower alpha olefins (C2 to C8) is less than a comparableplant based on conventional single stage vertical reactors deployed inseries to accomplish the same number of gas recycle zones. The savingsoccurs from the use of a single rector shell instead of multiple unitsto accommodate each zone. The elimination of the accessory equipmentrequired between reactors further reduces the capital equipment cost.

A typical polymerization, a propylene-ethylene co-polymer, to beproduced in the three zone reactor of FIG. 1, is summarized in thefollowing example. The yield of polymer per zone is estimated based onmaterial balance considerations, and polymerization rate information:

EXAMPLE 1

The co-polymer to be prepared is a bimodal propylene based ethyleneco-polymer:

The first gas recycle feed to Zone 1 has the following composition:

    ______________________________________                                                    Volumer Percent                                                   ______________________________________                                        Ethylene      --                                                              Propylene     82.5                                                            Hydrogen      17.5                                                            Pressure      300 PSI                                                         Temperature   65° C.                                                   ______________________________________                                    

Catalyst System

A hetrogeneous supported transition metal catalyst with an activator(alkyl) and electron donor.

The homopolymer formed and transported (C₃ H₆)×--82 lbs/hr.

The second gas recycle feed to Zone 2 has the following composition:

    ______________________________________                                                    Volume Percent                                                    ______________________________________                                        Ethylene      14.1                                                            Propylene     69.2                                                            Hydrogen      16.7                                                            ______________________________________                                    

The co-polymer formed

(C₂ H₄)×--15 lbs/hr. --18.3 weight percent

(C₃ H₆)×--67 lbs/hr. --81.7 weight percent.

The total solid formed and transported

(C₂ H₄)×--15 lbs/hr. --9.3 weight percent

(C₃ H₆)×--149 lbs/hr. --90.8 weight percent

The third gas recycle feed to Zone 3 has the following composition:

    ______________________________________                                                    Volume Percent                                                    ______________________________________                                        Ethylene      15.3                                                            Propylene     36.1                                                            Hydrogen      48.6                                                            ______________________________________                                    

The co-polymer formed

(C₂ H₄)×--29 lbs/hr. --35.4 weight percent

(C₃ H₆)×--53 lbs/hr. --64.6 weight percent

The total solids formed and transported

(C₂ H₄)×--44 lbs/hr. --17.9 weight percent

(C₃ H₆)×--202 lbs/hr. --82.1 weight percent

The total chemically blended polymer produced --246 lbs/hr.

For this example of the three zone reactor shown in FIG. 1, each zone isshown with three stage baffles forming four stages in each zone.

The particle residence time distribution for four stages within a zoneis shown in FIG. 4 as a distribution of residence time around theaverage residence time in the zone.

The particle residence time distribution through the three zonescomprising twelve stages is shown in FIG. 5 as a distribution ofresidence time around the average residence time in the reactor.

We claim:
 1. A fluidized bed apparatus suitable for use inpolymerization reactions comprised of:a) a single horizontal fluid bedreactor vessel; b) a gas distributor plate extending horizontally withinthe vessel and being constructed and arranged for passage of gastherethrough for fluidizing particulate material; c) an inlet meanspermitting the introduction into the vessel of solid particulatematerials utilized in the polymerization reactors; d) zone dividingwalls which divide the vessel into a plurality of zones and which extendsubstantially perpendicular to and above and below the distributorplate; e) baffles within each zone which divide the zones into aplurality of stages; f) the baffles having apertures for permittingpolymerized material to flow and be introduced into the next downstreamstage by fluidized horizontal flow; g) at least one zone dividing wallhaving an aperture permitting a polymerized material to be introducedinto the next downstream zone by fluidized horizontal flow; h) inletmeans associated with each zone for permitting entry of a gaseouscomponent capable of being polymerized into each stage and in such amanner through the distributor plate to maintain fluidization integrityof the particulate material and particles as they are transportedbetween stages and between zones; i) gas outlet means associated witheach zone for removing the gaseous component from each zone; j) outletmeans permitting the removal of polymerized material from the vessel;and k) recycling means for recycling the gaseous monomer exiting throughthe gas outlet means, said means being in communication with the inletmeans for introducing gaseous monomer to each stage, said recyclingmeans being individual for each of the inlet means; l) gaseous supplymeans separate and independent for each zone; m) said inlet means beingfurther in communication with the gaseous supply means.
 2. The fluidizedbed apparatus as set forth in claim 1 wherein the apertures in the zonedividing walls are selectively sized and located in order to keep gasphase mixing through the slots to less than the range of 3% to 5%. 3.The fluidized bed apparatus as set forth in claim 1 wherein thepolymeric solid material flows through apertures which arepreselectively closed on a timed cycle by closure means to reduce theextent of gas phase mixing through the apertures to less than 2%.
 4. Thefluidized bed apparatus as set forth in claim 1 wherein the aperturesupon the baffles are located on alternate outer edges of the baffles tocreate a serpentine course of flow for the polymeric material.
 5. Thefluidized bed apparatus as set forth in claim 1 wherein the zonedividing walls substantially seal a particular zone from its adjacentzone or zones.
 6. The fluidized bed apparatus as set forth in claim 1wherein the gaseous supply means for each zone is comprised of aplurality of gas lines permitting selection of a gaseous monomercomposition individual to each zone.
 7. The fluidized bed apparatus ofclaim 6 wherein the gaseous component individual to each zone differswith respect to at least one other zone.
 8. The fluidized bed apparatusas set forth in claim 1 wherein the number of baffles present withineach zone is sufficient to cause a plug flow profile through thereactor.
 9. A fluidized bed apparatus suitable for use in polymerizationreactions comprised of:a) a single horizontal fluidized bed reactorvessel; b) a gas distributor plate extending horizontally within thevessel and being constructed and arranged for passage of gastherethrough for fluidizing particulate material; c) an inlet meanspermitting the introduction into the vessel of solid particulatematerials utilized in the polymerization reactions; d) zone dividingwalls which divide the vessel into a plurality of zones and which extendsubstantially perpendicular to and above and below the distributorplate; e) baffles within each zone which divide the zones into aplurality of stages; f) the baffles having apertures for permittingpolymerized material to be transported due to fluidized gravity flow ofpolymerized material in the form of growing polymer particles andpermitting the polymerized material to be introduced into the nextdownstream stage by fluidized horizontal flow; g) at least one zonedividing wall having an aperture permitting the polymerized material tobe introduced into the next downstream zone by fluidized horizontalflow; h) inlet means associated with each zone for permitting entry of agaseous component capable of being polymerized into each stage and insuch a manner through the distributor plate to maintain fluidizationintegrity of the particulate material and particles as they aretransported between stages and between zones; i) gas outlet meansassociated with each zone for removing the gaseous component from eachzone; j) outlet means permitting the removal of polymerized materialfrom the vessel; and k) recycling means for recycling the gaseousmonomer exiting through the gas outlet means, said recycling means beingin communication with the inlet means for introducing gaseous monomer toeach stage, said recycling means being individual for each of the inletmeans; l) gaseous supply means separate and independent for each zone;m) said inlet means being further in communication with the gaseoussupply means.
 10. A fluidized bed apparatus suitable for use inpolymerization reactions comprised of:a) a single horizontal fluidizedbed reactor vessel; b) a gas distributor plate extending horizontallywithin the vessel and being constructed and arranged for passage of gastherethrough for fluidizing particulate material; c) an inlet meanspermitting the introduction into the vessel of solid particulatematerials utilized in the polymerization reactions; d) zone dividingwalls which divide the vessel into a plurality of zones and which extendsubstantially perpendicular to and above and below the distributorplate; e) baffles within each zone which divide the zones into aplurality of stages; f) the baffles having apertures for permittingpolymerized material to flow and be introduced into the next downstreamstage by fluidized horizontal flow; g) at least one zone dividing wallhaving an aperture permitting the polymerized material to be introducedinto the next downstream zone by fluidized horizontal flow; h) inletmeans associated with each zone for permitting entry of a gaseouscomponent capable of being polymerized into each stage and in such amanner through the distributor plate to maintain fluidization integrityof the particulate material and particles as they are transportedbetween stage and between zones; i) gas outlet means associated witheach zone for removing the gaseous component from each zone and heatassociated with the polymerization reaction; j) outlet means permittingthe removal of polymerized material from the vessel; and k) recyclingmeans for recycling the gaseous monomer exiting through the gas outletmeans, said recycling means being in communication with the inlet meansfor introducing gaseous monomer to each stage, said recycling meansbeing individual for each of the inlet means, said recycling means beingprovided with cooling means for reducing the temperature of the gaseousmonomer; l) gaseous supply means separate and independent for each zone;m) said inlet means being further in communication with the gaseoussupply means.
 11. A fluidized bed apparatus suitable for use inpolymerization reactions comprised of:a) a single horizontal fluidizedbed reactor vessel; b) a gas distributor plate extending horizontallywithin the vessel and being constructed and arranged for passage of gastherethrough for fluidizing particulate material; c) an inlet meanspermitting the introduction into the vessel of solid particulatematerials utilized in the polymerization reactions; d) zone dividingwalls which divide the vessel into a plurality of zones and which extendsubstantially perpendicular to and above and below the distributorplate; e) baffles within each zone which divide the zones into aplurality of stages; f) the baffles having apertures for permittingpolymerized material to flow and be introduced into the next downstreamstage by fluidized horizontal flow; g) at least one zone dividing wallhaving an aperture permitting the polymerized material to be introducedinto the next downstream zone by fluidized horizontal flow; h) inletmeans associated with each zone for permitting entry of a gaseouscomponent capable of being polymerized into each stage and in such amanner through the distributor plate to maintain fluidization integrityof the particulate material and particles as they are transportedbetween stages and between zones; i) gas outlet means associated witheach zone for removing the gaseous component from each zone; j) outletmeans permitting the removal of polymerized material from the vessel;and k) recycling means for recycling the gaseous monomer exiting throughthe gas outlet means, said recycling means being in communication withthe inlet means for introducing gaseous monomer to each stage, saidrecycling means being individual for each of the inlet means; l) gaseoussupply means separate and independent for each zone, the gaseous supplymeans being comprised of a plurality of gas lines permitting selectionof at least one gaseous monomer individual to each zone: m) said inletmeans being further in communication with the gaseous supply means. 12.A fluidized bed apparatus suitable for use in polymerization reactionscomprised of:a) a single horizontal fluidized bed reactor vessel; b) agas distributor plate extending horizontally within the vessel and beingconstructed and arranged for passage of gas therethrough for fluidizingparticulate material; c) an inlet means permitting the introduction intothe vessel of solid particulate materials utilized in the polymerizationreactions; d) zone dividing walls which divide the vessel into aplurality of zones and which extend substantially perpendicular to andabove and below the distributor plate; e) baffles within each zone whichdivide the zones into a plurality of stages; f) the baffles havingapertures for permitting polymerized material to be transported due tofluidized gravity flow of polymerized material in the form of growingpolymer particles and permitting the polymerized material to beintroduced into the next downstream stage by fluidized horizontal flow;g) at least one zone dividing wall having an aperture permitting thepolymerized material to be introduced into the next downstream zone byfluidized horizontal flow; h) inlet means associated with each zone forpermitting entry of a gaseous component capable of being polymerizedinto each stage and in such a manner through the distributor plate tomaintain fluidization integrity of the particulate material andparticles as they are transported between stages and between zones; i)gas outlet means associated with each zone for removing the gaseouscomponent from each zone and heat associated with the polymerizationreaction; j) outlet means permitting the removal of polymerized materialfrom the vessel; and k) recycling means for recycling the gaseousmonomer exiting through the gas outlet means, said recycling means beingin communication with the inlet means for introducing gaseous monomer toeach stage, said recycling means being individual for each of the inletmeans, said recycling means being provided with cooling means forreducing the temperature of the gaseous monomer; l) gaseous supply meansseparate and independent for each zone, the gaseous supply means beingcomprised of a plurality of gas lines permitting selection of at leastone gaseous monomer individual to each zone; m) said inlet means beingfurther in communication with the gaseous supply means.